Seed pre-soak technology with a drop of hematite nanoparticle fertilizer for increased plant growth

Abstract

A method for enhancing plant growth by pre-soaking a seed or plant material to be germinated with a drop of an iron oxide nanoparticle solution or dispersion is described. Pre-soaking the seed or other plant material with the nanoparticle solution or dispersion can, among other things, increase the growth rate, life span, fruit production of the plants grown from the pre-soaked seed or other material. Also described are the iron oxide nanoparticles themselves, and methods of preparing the iron oxide nanoparticles. The size, morphology, and surface charge of the iron oxide nanoparticles can be influenced by polymeric organic ligands used in the preparation of the nanoparticles.

1 . A method of enhancing soybean plant growth, the method comprising contacting a soybean seed with a single drop of an aqueous composition comprising an iron oxide nanoparticle for a period of time prior to planting said soybean seed, wherein the single drop is of a volume of 0.03 milliliters (mL) to about 0.07 mL. 
     
     
         2 . The method of  claim 1 , wherein the period of time is sufficient for the soybean seed to germinate. 
     
     
         3 . The method of  claim 2 , wherein the period of time is about 2 days to about 5 days. 
     
     
         4 . The method of  claim 1 , wherein the soybean seed is placed on a wetted cellulosic substrate prior to or during said period of time. 
     
     
         5 . The method of  claim 1 , wherein the seed is a soybean seed of a soybean plant species planted for food or for bio-energy production. 
     
     
         6 . (canceled) 
     
     
         7 . The method of  claim 1 , wherein the drop has an iron oxide nanoparticle concentration of between about 0.01 grams per liter (gL −1 ) and about 1.5 gL −1 . 
     
     
         8 . The method of  claim 1 , wherein the drop comprises about 10 micrograms (μg) to about 75 μg of Fe. 
     
     
         9 . The method of  claim 1 , wherein the iron oxide nanoparticle comprises a core or a coating layer comprising hematite. 
     
     
         10 . The method of  claim 1 , wherein the iron oxide nanoparticle comprises one or more polymeric organic ligands. 
     
     
         11 . The method of  claim 10 , wherein the one or more polymeric organic ligands are selected from polyvinylpyrrolidone (PVP) and polyethyleneimine (PEI). 
     
     
         12 . The method of  claim 11 , wherein the iron oxide nanoparticle has an average hydrodynamic diameter of about 50 nanometers (nm) to about 250 nm as measured by dynamic light scattering. 
     
     
         13 . The method of  claim 11 , wherein the iron oxide nanoparticle has a surface charge of about −10 mV to about 40 mV. 
     
     
         14 . The method of  claim 13 , wherein the iron oxide nanoparticle has a surface charge of about 1.0 mV to about 35 mV. 
     
     
         15 . The method of  claim 11 , wherein the iron oxide nanoparticle is prepared from a reaction mixture comprising an iron precursor and one or both of PVP and PEI, and wherein said reaction mixture comprises about 0 moles to about 0.04 moles of PVP per mole of iron precursor and about 0 moles to about 0.01 moles of PEI per mole of iron precursor. 
     
     
         16 . The method of  claim 15 , wherein the iron precursor is iron (III) acetylacetonate (Fe(acac) 3 ). 
     
     
         17 . The method of  claim 15 , wherein the reaction mixture comprises about 0 moles to about 0.030 moles of PVP per mole of iron precursor and about 0 moles to about 0.010 moles of PEI per mole of iron precursor. 
     
     
         18 . The method of  claim 15 , wherein the iron oxide nanoparticle is prepared from a reaction mixture selected from the group consisting of a reaction mixture comprising about 0.035 moles of PVP and about 0.0025 moles of PEI per mole of iron precursor; a reaction mixture comprising about 0.030 moles of PVP and about 0.0025 moles of PEI per mole of iron precursor; a reaction mixture comprising about 0.005 moles of PVP per mole of iron precursor; a reaction mixture comprising about 0.005 moles of PVP and about 0.00415 moles of PEI per mole of iron precursor; and a reaction mixture comprising about 0.005 moles of PEI per mole of iron precursor. 
     
     
         19 . The method of  claim 10 , wherein the iron nanoparticle is prepared from a reaction mixture comprising an iron precursor and the one or more polymeric organic ligands, and wherein a ratio P:C of moles of iron precursor to total moles of said one or more polymeric organic ligands is about 20 or more. 
     
     
         20 . The method of  claim 19 , wherein the ratio P:C is about 30 to about 200. 
     
     
         21 . The method of  claim 1 , wherein the soybean seed is planted in a soil that has been exposed to a traditional fertilizer or wherein plants growing from said soybean seed are treated with a traditional fertilizer. 
     
     
         22 . The method of  claim 1 , wherein enhancing soybean plant growth comprises one or more of increasing growth rate, increasing plant height, increasing root growth, increasing leaf production, increasing fruit production, increasing the rate of fruit production, increasing seed pod production, increasing plant survival rate, and increasing plant life span compared to a plant from an untreated seed. 
     
     
         23 . (canceled) 
     
     
         24 . (canceled) 
     
     
         25 . The method of  claim 1 , wherein the seed is a soybean seed, and the method provides a soybean plant with a growth rate about 150% that of a soybean plant grown from an untreated soybean seed. 
     
     
         26 . (canceled) 
     
     
         27 . A fertilizer composition comprising an iron oxide nanoparticle, wherein said iron oxide nanoparticle comprises iron oxide and one or more polymeric organic ligands, and wherein the ratio of moles of iron to moles of polymeric organic ligand is about 30 to about 200; and wherein the iron oxide nanoparticle has a surface charge of about 1.0 mV to about 35 mV. 
     
     
         28 . The fertilizer composition of  claim 27 , wherein the iron oxide nanoparticle has a hydrodynamic diameter of about 50 nanometers (nm) to about 250 nm as measured by dynamic light scattering. 
     
     
         29 . The fertilizer composition of  claim 27 , wherein the iron oxide nanoparticle comprises hematite. 
     
     
         30 . The fertilizer composition of  claim 27 , wherein the one or more polymeric organic ligands are selected from the group consisting of polyvinylpyrrolidone (PVP) and polyethyleneimine (PEI). 
     
     
         31 . The fertilizer composition of  claim 30 , wherein the iron oxide nanoparticle is prepared from a reaction mixture comprising an iron precursor and one or both of PVP and PEI, and wherein said reaction mixture comprises about 0 moles to about 0.03 moles of PVP per mole of iron precursor and about 0 moles to about 0.01 moles of PEI per mole of iron precursor. 
     
     
         32 . The fertilizer composition of  claim 31 , wherein the iron precursor is iron (III) acetylacetonate (Fe(acac) 3 ). 
     
     
         33 . The fertilizer composition of  claim 31 , wherein the nanoparticles are prepared from a reaction mixture selected from the group consisting of a reaction mixture comprising about 0.030 moles of PVP and about 0.0025 moles of PEI per mole of iron precursor; a reaction mixture comprising about 0.005 moles of PVP per mole of iron precursor; a reaction mixture comprising about 0.005 moles of PVP and about 0.00415 moles of PEI per mole of iron precursor; and a reaction mixture comprising about 0.005 moles of PEI per mole of iron precursor. 
     
     
         34 . The fertilizer composition of  claim 27 , wherein the iron oxide nanoparticle is provided in an aqueous solution or dispersion. 
     
     
         35 . The fertilizer composition of  claim 34 , wherein the concentration of iron oxide nanoparticle in the aqueous solution or dispersion is about 0.010 grams per liter (gL −1 ) to about 1.5 gL −1 . 
     
     
         36 . A method of preparing an iron oxide nanoparticle fertilizer composition, the method comprising:
 (a) dissolving one or more polymeric organic ligands in a solvent, wherein the solvent comprises a polyol to provide a ligand solution;   (b) adding an iron precursor to the ligand solution to provide a reaction mixture; and   (c) heating the reaction mixture under an inert atmosphere for a period of time to provide iron oxide nanoparticles.   
     
     
         37 . The method of  claim 36 , wherein the polyol is a diol. 
     
     
         38 . The method of  claim 37 , wherein the diol is triethylene glycol. 
     
     
         39 . The method of  claim 36 , wherein the one or more polymeric organic ligands are selected from polyvinylpyrrolidone (PVP) and polyethyleneimine (PEI). 
     
     
         40 . The method of  claim 36 , wherein the iron precursor is iron (III) acetylacetonate. 
     
     
         41 . The method of  claim 36 , wherein the reaction mixture is heated to about 290° C. 
     
     
         42 . The method of  claim 36 , wherein the period of time is about one hour. 
     
     
         43 . The method of  claim 36 , wherein the ratio of moles of iron precursor in the reaction mixture to total moles of polymeric organic ligand is about 30 or more. 
     
     
         44 . The method of  claim 43 , wherein the ratio of moles of iron precursor in the reaction mixture to total moles of polymeric organic ligand is about 30 to about 200. 
     
     
         45 . The method of  claim 36 , wherein the reaction mixture comprises about 0 moles to about 0.03 moles of PVP per mole of iron precursor and about 0 moles to about 0.01 moles of PEI per mole of iron precursor. 
     
     
         46 . The method of  claim 45 , wherein the reaction mixture is selected from the group consisting of a reaction mixture comprising about 0.030 moles of PVP and about 0.0025 moles of PEI per mole of iron precursor; a reaction mixture comprising about 0.005 moles of PVP per mole of iron precursor; a reaction mixture comprising about 0.005 moles of PVP and about 0.00415 moles of PEI per mole of iron precursor; and a reaction mixture comprising about 0.005 moles of PEI per mole of iron precursor.